A former sergeant with the Tombstone Marshal’s Office has voluntarily relinquished his law enforcement certification following an investigation that revealed an obsession with a woman in the town, comments about disturbing practices against females and an admission to his superiors that he was having sex on the job, documents show.

According to the Arizona Peace Officer Standards and Training Board, Travis Mattern, a former sergeant with the Marshal’s Office, gave up his certification recently. Certification functions similarly to a professional license. The certificate is issued by a state government as a requirement to legally work as a police officer in a particular state.

Mattern’s case came up in front of the board last month, and members voted to proceed with a query to determine whether his certification should be stripped, said Cochise County Sheriff Mark Dannels, chairman of the panel. That investigation became unnecessary once Mattern voluntarily gave up the certification.

A six-page internal investigation of the former sergeant released recently to the Herald/Review shows a pattern of disturbing behavior by Mattern that included his obsession with a woman who worked at a popular Tombstone bar. According to the investigation, Mattern would follow the woman home, would park near her car outside the saloon, wait for her and would come inside the business and hang out at the bar while she worked.

In January while on duty, Mattern sent the woman an explicit text message describing how they would have sex. When the woman told him the message was a bit much and that she would not cheat on her partner, Mattern told her he enjoyed writing that kind of prose and that he had been published in Penthouse magazine several years ago, the investigation shows.

The investigation also reveals that Mattern told another female he enjoyed inflicting pain on women, particularly “cutting women and putting salt or lemon juice in their wounds,” among other practices.

The former cop admitted to Tombstone Marshal Jim Adams that he had sex on top of his patrol car while he was on duty, the investigation says.

A couple of days before Mattern resigned, Adams said he was riding with a female captain with the Arizona Rangers who mentioned Mattern had asked her “inappropriate questions of a sexual nature” regarding a three-way swinger’s club in the area, the investigation shows. The captain said Mattern asked her if she and her husband “were interested in things like that.”

Adams said Mattern resigned in late February after the woman who worked at the bar filed a complaint against him. The woman told Adams she was afraid of Mattern and that he was “creepy,” the investigation shows.

In the investigation document, Adams stated he informed the offices of the Cochise County Attorney and the Tombstone City Attorney of Mattern’s resignation because “ ... it may impact cases involving Mattern’s involvement as a foundational witness.”

The allegations lodged against Mattern — conduct unbecoming an officer and immoral conduct — were sustained.

Mattern could not be reached for comment. A number listed for him continuously rings busy.